heh .. I rove in the VHF contests with pretty high power on the 'low'
bands, 400W on 6 and 2 and 200W on 222 and 432, but I'm interested in
building a set of four pallets with the new LDMOS 1KW devices. The
problem with these devices in a roving situation is getting a source
of 50V to recharge whatever battery bank I end up using to power them.
I've been considering modifying an alternator to remove all of the
regulating/rectifying stuff and just bring out the three phases and
the field to an external box. I could then either (a) put in a trio of
transformers to bring the voltage up to 50, possibly deriving
regulator input from the 50V side or (b) setting up switching to
connect the output to either the car or the HV bank and changing the
field as required for the desired voltage.
Bill, do you know of any reference works or articles that discuss
these types of modifications? I've looked around a bit and have not
had much luck ..
de w1rt/john
On Mon, Aug 27, 2012 at 12:34 PM, Bill Fuqua <wlfuqu00@uky.edu> wrote:
> Alternators are interesting devices. Today they have internal
> regulators which control the field current to regulate the output voltage.
> They have to charge batteries and operate lights and other equipment even
> at idle. Alternators are limited mostly by the heating of the
> stator windings which is current squared times the windings resistance. If
> you do away with the regulator and provide your own excitation
> to the field ( rotor) you can get much more output voltage. You can get 120
> or more volts DC, or AC if diodes are removed from them and draw the same
> current. This
> used to be done years ago when folks wanted to run their electric chain saw
> or skill saws off of their car's alternator. They had universal
> winding motors. Also the silicon rectifiers had sufficient reverse
> polarization to handle 120VDC output. They probably use Schottky today
> which may not.
> By the way, they do have quite a high frequency output.
> 73
> Bill wa4lav
>
>
> At 05:41 AM 8/27/2012 -0700, Jim Hoge wrote:
>
>
>>Don,
>>
>>That's the exception. I've heard the claims from some who run stock that
>>they are capable of such numbers. I had a boss who was an ardent cber ask
>>me to fix his mobile solid state amp. I said I would take a look at it.
>>After all, I was curious. I had no intention of fixing it for him though.
>>The math said there was no way he could get 500 watts out with only a 20
>>amp fuse in the 12 volt supply lines, even IF the amp ran at an efficiency
>>of 100%. Who only knows how over driven the amp must be and I'd hate to
>>see the spectrum analyzer under such conditions. BTW, it was a blown
>>transistor on the input side (2x4 configuration). Gee, I wonder how that
>>happened. I gave the amp back to him and said I couldn't find the problem.
>>
>>
>>Gotham couldn't hold a candle to some of these guys.
>>
>>73,
>>Jim W5QM
>>
>>
>>
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>
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